In the case of a magnetic recording system, when the recording density becomes high, magnetic bits tend to undergo influence of external temperature or the like. This requires use of a recording medium having a high coercive force, but when using such a recording medium, a magnetic field applied during recording becomes also high. The upper limit of magnetic field generated from the magnetic head is determined by the saturation magnetic flux density, but a magnetic field thereof approaches the material limitation value, whereby no drastic increase can be expected. Herein, proposed is a system in which stability in recorded magnetic bit is secured when heating is applied locally during recording to reduce the magnetization, and recording is performed when the coercive force becomes small, followed by termination of heating via naturally cooling. This system is called a thermally assisted magnetic recording system.
In the case of the thermally assisted magnetic recording system, it is preferred that a recording medium is instantaneously heated. For this reason, heating is conventionally conducted by utilizing absorption of light, and a system in which light is utilized for heating is called an optically assisted magnetic recording system.
In the optically assisted magnetic recording system, a light spot can be reduced in size by using waveguides having high relative refractive index differences, but the light spot can only be reduced to a limited degree of roughly λ (wavelength of light to be used)/n (refractive index). For this reason, the optically assisted magnetic recording system can not be applied sufficiently to a light spot of roughly 20 nm desired to be used for very high density recording. In contrast, there is a method of using near field light as a method of further reducing a light spot in size. The light spot diameter obtained from the near field light is determined mainly by the nose shape of a sharpened fine metallic structure body (called a plasmon probe), and the diameter can be applied for the very high density recording at several tens of nanometers in size.
Patent Document 1 has disclosed recording head which generates near field light via collection of laser light to a metal pin by a wave guide (Planar Solid Immersion Mirror, also referred to as PSIM), for example.
It is disclosed in Patent Document 2 that concerning a plasmon probe, the size is arranged to be smaller than an exposure light spot, and material, shape and dimension of the plasmon probe are designed so as to generate plasmon resonance to operate a near field light generator exhibiting high resolution and high efficiency.